[inquest]

All states will have to recognize those marriages under the full faith and credit clause.

That's not true unless Congress mandates it to be true. I mean, would a license to buy and sell firearms in Virginia be binding in Massachusetts?

[colorado tanker]

It's in the Constitution.

Article IV

Section 1. Full faith and credit shall be given in each state to the public acts, records, and judicial proceedings of every other state. And the Congress may by general laws prescribe the manner in which such acts, records, and proceedings shall be proved, and the effect thereof.

This is why you can get married in Nevada and it will be recognized in your home state.